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The primary roles of the digestive system are:
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- breakdown of food into nutrients
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- absorption of nutrients
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- elimination of solid waste products
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Digestion is the process of breaking down large food molecules into nutrients that the body can use
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Absorption is the uptake and removal of nutrients from the digestive tract.
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- The digestive tract is also called the gastrointestinal tract (GI), alimentary canal, or gut
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# The GI tract
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## Order
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1. Mouth
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1. Digestion starts here for carbohydrates and fats (not proteins)
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2. Salivary glands are structures that produce saliva and secrete the fluid in the oral cavity
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3. Saliva is the watery fluid that contains mucus and enzymes
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1. Lysozyme - Destroys some bacteria that are in the food or mouth
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2. Salivary Amolase
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3. Lingual Lipase
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4. Taste buds have specialized cells that help distinguish five basic tastes
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5. You lose taste buds as we age. Older people have fewer taste buds than younger people.
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2. Esophagus*
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1. The esophagus is a flap of tough tissue that p
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3. Stomach*
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4. Small intestine (DJI)
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1. Duodenum
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2. Jejunum
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3. ileum*
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5. Large intestine
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6. Rectum
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7. Anus
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## Sphincters
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Sphincters are thickened regions of circular muscle that control the flow of contents at various points in the GI tract.
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- Contracted:
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- Passageway closed
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- Flow is restricted
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- Essential for normal digestion and absorption
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There are 3 main sphincters associated with digestion:
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1. Gastroesophageal/lower esophageal/cardiac - connects the esophagus to the stomach
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2. Pyloric - connects the stomach to the duodenum (small intestine)
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3. ileocecal valve - Connects the small intestine to the large intestine
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The upper esophageal sphincter is at the top of the esophagus (not as important).
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# Digestion
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**Mechanical digestion refers to the physical treatment that food undergoes** while it is in the intestinal tract
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Chemical digestion refers to the breakdown of large molecules in food into smaller components, primarily by the action of **enzymes**.
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- Enzymes are a protein that speeds up the rate of a chemical reaction without being altered in the process.
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- Enzymes usually end in -ase and begin with the name of whatever they are working to digest:
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- Amylase digests amylose
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- Maltase digests maltose
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